I have setup two monitors in my system. One is powered by the HDMI port and the other one is powered by the normal Analogue port of the same GPU (Nvidia Ge-force 210). I just setup twin display in Nvidia settings but can't see the cinnamon's panel on the second monitor. How to fix this?

Far as I know with TwinView you have the choice of making one monitor be the "primary Display for X screen" and this is the one that gets the panel. I have not found a way to have panel span both monitors, or have separate one on each.

Look nvidia settings in the menu for these options. It takes a bit of fiddling to get the right one.. in my experience, had to explicitly set this montior "right of" and the other one "left of" to get them right way round.